[The development of beta-carotenemia in dairy cows 1975-1987].

On investigation of beta-carotene levels in the blood plasma of 9193 cows in the first and second phases of lactation, and in the eight, ninth months, and to the tenth mid-month of their pregnancy showed the same dynamics in beta-carotinaemia development in all groups, with a wave-like tendency to decrease. The lowest beta-carotene values were recorded during the 1985-1986 winter season and in the following 1986 summer season. Beta-carotene levels also remained low during the subsequent winter and summer feeding season. Different beta-carotene concentrations in the blood plasma were repeatedly found in the phases of lactation reproduction cycle. Increases in the milk production and deteriorated reproduction indicators were recorded in the cows at the time of a steep decrease in beta-carotene concentrations in the blood plasma. The causes of decreasing beta-carotene concentrations in the cow blood plasma are discussed.